He said Watson's safety has been jeopardized in the past when such information became public. Offshore companies, such as the one Watson set up, do not publish shareholder details.

Some U.K. media reported that the actress had set up the company to buy a property in London. Watson's spokesman declined to comment.

British newspaper The Spectator first found Watson's name in a public database of individuals and entities that have alleged links to Mossack Fonseca. The database, released by the the International Consortium of Investigative Journalists, details ties between 368,000 people and nearly 320,000 offshore entities.

It is based on a leak of over 11 million documents from the Panama-based law firm.

According to the leaked data, Watson set up a company called Falling Leaves Ltd in 2013 in British Virgin Islands. The U.K. overseas territory in the Caribbean has been identified by the European Commission as a tax haven.

There are many legitimate reasons for opening an offshore bank account. Wealthy people do it to better manage their investment portfolios or protect their assets. Offshore accounts can also help the rich pay less tax -- legally.